A conventional thermal infrared ray detector includes, for example, that described in Patent Document 1 or 2. Patent Document 1 has disclosed a pyroelectric infrared ray solid-state image pickup device. An infrared ray absorbing film used in the device has a laminated structure composed of an organic layer sensitive in a wide range of infrared ray and an SiO2 layer high in absorption rate in the vicinity of a wavelength of 10 μm.
Further, Patent Document 2 has disclosed a thermal infrared ray sensor. The sensor has a multi-structured infrared ray absorbing film containing a metal thin film at the lowermost layer. The metal thin film is greater in reflection rate of infrared ray than in transmission rate of infrared ray, attempting to increase the absorption rate of infrared ray on other layers by allowing infrared ray in an attempt to transmit through the other layers to reflect on the metal thin film.    Patent Document 1: Japanese Patent No. 2523895    Patent Document 2: Japanese Patent No. 3608427